Prevention of salt water encroachment into fresh water aquifers

ABSTRACT

THE ADVANCE OF SALINE WATER INTO FRESH WATER AQUIFERS IS INHIBITED BY INJECTING INTO THE AQUIFER, PREFERABLY IN ADVANCE OF THE INTRUDING SALT WATER, A MICELLAR SOLUTION COMPRISING PREFERABLY A LOW EQUIVALENT WEIGHT PETROLEUM SULFONATE. SUCH A MICELLAR SOLUTION, INTER ALIA, BECOMES VISCOUS UPON CONTACT WITH SALINE WATER AND INHIBITS THE FURTHER ENCROACHMENT OF ADDITIONAL SALINE WATER.

FIPT912 :SA LT WATER BODY ORIGINAL FRESH WATER AQUlFER"-NOW INVADED BYSALT WATER William C. Toscli Parker, Colo.

Nov. 5, 1969 June 28, 1971 Marathon Oil Company Findlay, Ohio Appl. No.Filed Patented Assignee PREVENTION OF SALT WATER ENCROACHMENT INTO FRESHWATER AQUIFERS 7 Claims, 2 Drawing Figs.

Int. Cl Elm} 33/158 Field of 166/268,

Primary Examiner-Stephen J. Novosad Attorneys-Joseph C. Herring, RichardC. Wilson, Jr. and

Jack L. Hummel ABSTRACT: The advance of saline water into fresh wateraquifers is inhibited by injecting into the aquifer, preferably inadvance of the intruding salt water, a micellar solution comprisingpreferably a low equivalent weight petroleum sulfonate. Such a micellarsolution, inter alia, becomes viscous upon contact with saline water andinhibits the further encroachment of additional saline water.

FRESH WATER AQUIFER I'J BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to inhibiting salt water encroachmentinto fresh water aquifers. This is accomplished by injecting into theaquifer a micellar solution which has the capability of becoming aviscous liquid upon contact with saline water. The viscous liquidinhibits the advance of the saline water.

2. Description of the Prior Art in many areas contiguous to salt waterbodies, e.g. Southern California, fresh water is being pumped fromsubterranean formations (e.g. aquifers) at a rate faster than it can beregenerated, thereby lowering the water tables and allowing salinewaters from adjacent salt water bodies to enter the fresh wateraquifers. Thus saline water is permitted to flow inland to replace thedisplaced fresh water. The inflowing saline waters mix with the freshwaters, rendering them brackish and unsuitable for certain r ses.

' The intrusion of saline water into fresh water aquifers takes placegradually, however once saline water has intruded, it is seldom possibleto effectively repulse its detrimental effects.

Salt water intrusion can occur when the fresh water level in the aquiferdrops, thereby lowering the fresh water table and permitting salinewater to flow into the aquifers remaining fresh water. Also, loweringthe fresh water level can lower the hydrostatic head of the fresh waterbelow that of the saline water, resulting in the saline water displacingand contaminating the fresh water.

The prior art teaches, in U.S. Pat. No. 3,380,522, a method of stoppingthe horizontal advance of saline water into a fresh water aquifer byinjecting into the aquifer a slurry containing granular materials suchas reclaimed oil well drilling mud and sedimentary clay from the oceanfloor. The patent claims that such materials form an impermeablebridging mass in the aquifer and thereby block the intruding salinewater. DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of anearth formation having a fresh water aquifer, a body of saline waterrelated thereto and a cutoff established therein in accordance with thisinvention.

FIG; 2 is a diagrammatic plan view of the invention illustrating atypical application thereof.

In FIG. 1 a fresh water aquifer H-I-I'l-I' is illustrated. The aquiferis labeled H-I-I J J' in the plan view. The aquifer may be of any typeof water bearing and/or conducting formation with the arrow indicatingthe normal direction of flow of fresh water in the aquifer.

This invention establishes an impermeable or substantially impermeabledam or cutoff K extending transversely in or across the aquifer alongthe line DE in FIG. 2. That is, transverse to the direction of flow ofwater therethrough.

The damming or cutoff structure K is established in the aquifer byintroducing and depositing a micellar solution into the aquifer. LettersA, B, C represent typical water pumping wells,'or newly drilled wells,which according to the teachings of this invention, can be used toinject the micellar solution into damming position along the line DE inthe fresh water aquifer. Letters X, Y, and 2 represent water injectionwells presently employed in some encroachment inhibition systemsdiscussed in this application.

Methods of preventing salt water encroachment in areas such as southernCalifornia are depicted in FIGS. 1 and 2. Pumping wells A, B, C, etc.,are sunk into fresh water aquifers along the line DE, where saline waterhas intruded. A plurality of fresh water injection wells X, Y, Z aresunk into the fresh water aquifer upstream or ahead ofthe line to whichthe saline water has intruded. By pumping fresh water into the aquifersby means of the injection wells X, Y, Z and by extracting a like amountof water from the pumping wells A, B, C, it is sought to keep thatportion of the aquifer between the wells filled with fresh water and tomaintain the flow F, of such water downstream or in opposition to theflow S, of such intruding saline water, thereby stopping brineintrusion. To date, the effectiveness of the above-mentioned method isquestionable, as it requires constant injection of great quantities offresh water into the aquifer. Furthermore, due to the tendency of waterto seek out and establish channels in aquifers, it is anticipated thatthe end result will be the establishment of outflowing channels of freshwater in the aquifers between injection and pumping wells. The intrusionof saline water into the aquifers, between the fresh water channels willcontinue and this intrusion will eventually progress beyond or upstreamof the injection wells.

SUMMARY OF INVENTION Applicant has discovered a method of inhibitingsaline water intrusion into fresh water aquifers by injecting a micellarsolution into the aquifer, preferably between the fresh water and theintruding saline water.

When the saline water contacts the micellar solution, an increase inviscosity is realized. Again referring to FIGS. I and 2 it is seen thata slugging" effect can be accomplished to prevent encroachment of salinewater into the fresh water aquifer along the line DE. Also the micellarsolution can be used to provide a cutoff in a fresh water aquifer whichserves to dam the normal outward flow F of fresh water, thus, the waterlevel in the aquifer can be maintained at a sufficient head to opposeand overcome the intrusion of saline water S entering the aquiferdownstream from the cutoff. The micellar solution can also be used toplug an existing salt water aquifer.

DESCRIPTION OF THE INVENTION The micellar solution is comprised ofhydrocarbon, aqueous medium and surfactant. Optionally, cosurfactant(also identified as semipolar organic compound and cosolubilizer) and/orelectrolyte can be incorporated. Examples of volume amounts include fromabout 30 percent or less to about percent of hydrocarbon, from about 10percent to greater than about 60 percent water, at least about 4 percentsurfactant, from about 0.01 percent to about 20 percent cosurfactant,and from about 0.001 percent to about 5 percent by weight of electrolyte(based on the aqueous medium).

Examples of useful hydrocarbons include most petroleum basehydrocarbons, e.g. crude oil, fractions of crude oil such as gasoline,kerosene, crude column overheads, etc.; refined fraction of crude oilsuch as benzene, substituted aryl compounds, etc.; synthesizedhydrocarbons such as halogenated hydrocarbons, substituted aliphatic andaromatic compounds, etc.

Useful cosurfactants include alcohols, ketones, aldehydes, aminocompounds, esters and like materials containing up to 20 or more carbonatoms. Examples include ethanol,

isopropanol, iand n-butanol, amyl alcohols, hexanols,'

cyclohexanol, cresol, phenol, substituted phenols, and crude alcoholssuch as fusel oil.

The surfactant can be nonionic, cationic, and anionic. Examples ofuseful surfactants include those taught in U.S. Pat. No. 3,254,714 toGogarty, et al.

Preferably the surfactant is anionic, e.g. alkyl-aryl sulfonates,particularly alkyl-naphthenic monosulfonates, wherein the alkyl radialcontains from about 10 to about 20 carbon atoms. The sodium salts ofdialkylsuccinates are also desirable surfactants. More preferably, thesurfactant is a sodium or ammonium petroleum sulfonate having an averageequivalent weight within the range of from about 350 to about 525 It ispreferred that the alkyl radicals of the succinate compounds containfrom about 6 to about l0 carbon atoms.

The micellar solution can be injected into the aquifer at sufficientpressure to lift the overburden. The pressure can then be released andthe overburden will settle and exert its pressure onto the micellarsolution deposited in the aquifer so as to form a tight seal. However,in most applications the injection pressure will not exceed the"fracturing" pressure of the formation.

It is desired to use established wells A, B. C, along lines such as DEof FIG. 1 where it is desired to establish a cutoff in a fresh aquifer;however, wells can be drilled for injection purposes. The injection ofthe micellar solution into the aquifer line on which it is desired toestablish the cutoff. it is also to be understood that the micellarsolution can be introduced into the formation under considerablepressure so as to obtain the necessary penetration.

can be carried out in a sequential order or injected at one 5 it will beapparent that in practice, particularly in aquifers time. of greatvertical depth, the cutoff or cutoffs need not extend The above merelydescribes the typical preferred embodifrom the lower or substrata to theoverlying or superstrata. ments of carrying out the invention. Theinvention is not to be But, the cutofi(s) may be established to extendfrom the lower limited by these specific details; rather, allmodifications and or substrata upwardly, or from the upper to the lowerstrata, a variations obvious to those skilled in the art are meant to besufficient distance to inhibit or stop the flow of water in aporincluded within the invention as defined in the specification tion ofthe aquifer to a sufficient extent to change the water and appendedclaims. table necessary to stop saline water intrusion. This, of course,

depends upon the specific geology of the aquifer. EXAMPLE] 1mm: Micellarsolutions defined in Table l are prepared from am- I. A method ofinhibiting the advance of saline water into a monium petroleum sulfonate(average MW=410, about 62 substantially horizontally extending freshwater aquifer percent active sulfonate), water (contains indicatedsalinity), between substantially impermeable strata in the earth whichisoproponal and indicated hydrocarbon. Viscosities of the comprises,injecting into the aquifer a micellar solution capamicellar solutionsare indicated in Table 1. Upon contact with 0 ble of producing a viscousmixture upon contact with the saline water, the viscosities aredrastically increased as in- 2 saline water, said micellar solutionbecoming viscous upon dicated in Table 1: contact with the saline waterto establish a blocking material TABLE 1 Saline Water Hydrocarbon waterwith Final or Water, salinity, lsopropyl which micellar resultant vol.mg./100 alcohol, Sultanate, Vol. Viscosity solution is slug vis.,Micellar solution percent ml. water vol. percent vol. percent percentType cp., 72 F. contacted cp., 72 F.

20.4 830, NaC 2.0 13.7 24 HPW 1 ca. 500 29.4 420, NaCl 2.0 11.6 19. 7HPW 2 ca. 500 2.1. 6 420, NaCl 1.2 11.8 ca. 25 HPW 2 ca. 1,000 29.61,670, NaCl 1.2 11.8 ca. HPW 2 ca. 860 34.8 4.3, NBZSO! 0.5 8.1 50.2 HPW2 1,000

1 Stabilized Light Straight Run Gasoline.

'- Henry Plant Water (obtained from the Levi Henry lease near Robinson,Ill.) contains about 20,000 p.p.m. total dissolved solids.

The micellar solution is injected into the aquifer through a suitablewell structure. Upon contact with a brine solution it becomes veryviscous. Fresh water aquifers which are subject to saline waterintrusion are ordinarily relatively close to the earths surface. Hence,cost of drilling and establishing wells for the injection of micellarsolution should not be unduly prohibitive in the light of theconservation of the fresh water that is to be effected.

in the preferred embodiment of this invention, it is desired toestablish the cutoff along a line DE extending transverse to theaquifer. This can be accomplished using two wells such as AB, AC, BC,etc. One well is located at one end of the line DE along which it isdesired to establish the cutoff, and the other well is located at theother end of the line. One well is employed to inject the micellarsolution into the formation and the other is employed to pump water fromthe aquifer during the injection process. The pressure in the aquifer inand around the second or producing well opposite the first or injectionwell is lowered and the flow of water in the aquifer in close proximityto the second or producing well flows toward said producing well therebyinducing and causing the micellar solution injected into the first orinjection well to flow towards said second well. it is apparent that theprovision of the second producing well is effective to reduce to aminimum the required volume of micellar solution. In addition toreducing the costs, it provides a positive means of reading andcontrolling the process. The producing well can also become a micellarsolution injection well as the process is carried on. it is alsoapparent that the second producing well must be sufficiently close tothe injection well to obtain the desired lowering of pressure and thedesired direction of flow of water and micellar solution in theformation. Accordingly, in situations where it is desired to establish acutoff of considerable longitu dinal extent, a plurality ofwellsmay beused in series along the in the aquifer to inhibit the advance of theintruding saline water.

2. The method of claim 1 wherein said micellar solution is injected intothe aquifer through at least one injection well and positioned in theaquifer by controlling the removal of fluids from at least one otherwell in fluid communication with the aquifer so as to induce saidblocking material to flow into blocking position.

3. A method of inhibiting the advance of saline water into a fresh wateraquifer extending substantially horizontally between substantiallyimpermeable sub and superstrata in the earths formation and having atleast one injection means in fluid communication with the aquifer, themethod comprising injecting into the aquifer in advance of the intrudingsaline water a sufficient amount of micellar solution to form a bridgingmass traverse of the intruding saline water, permitting the saline waterto contact the micellar solution whereupon a viscous material is formedand the intrusion of saline water is inhibited.

' 4. The method of claim 3 wherein repeated amounts of micellar solutionare injected into the aquifer to maintain the viscous blocking effect.

5. The method of claim 3 wherein the micellar solution is oil-externaland is-prepared with a petroleum sulfonate having an average equivalentweight within the range of from about 350 to about 525.

6. The method of claim 3 wherein the micellar solution contains byvolume from about 30 percent to about percent hydrocarbons; from about10 percent to about greater than 60 percent water and at least about 4percent surfactant.

7. The method of claim'6 wherein the micellar solution contains fromabout 0.01 percent to about 20 percent cosurfactant and/or from about0.001 percent to about 5 percent of weight of electrolyte (based on theaqueous medium).

a 3 UMTED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3587 ,"7 3 7 Dated 6/2 8 /7l Invento (s) William C. Tosch It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Col. 2, line 62: Delete "radial" and insert --radical-.

Col. (Table I) line 8 Delete "830 ,NaC" and insert --830,NaCl--.

Signed and sealed this 2nd day of November 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,J'R. ROBERT GOTTSCHALK Attesting Officer- ActingCommissioner of Patents

